Sand core making machines are used to produce sand cores which in turn are subsequently used to produce cavities or recesses in cast parts. Generally, the material used for making a core is not only sand, it is a mixture comprising sand, preferably mixed with a kind of resin, although the cores made in this type of machines are commonly known as sand cores.
Machines of this type are normally included in installations comprising, in addition to one of these machines, another machine where casting is performed. In these installations the corresponding sand core produced in the sand core making machine is transported to another machine where casting is performed by suitable conveyance means. There are different types of conveyance means (such as robots or conveyor belts, for example) and machines to perform casting that are not described in detail as they are not an object of the invention.
In conventional sand core making machines, to perform said production the material for making the core is transferred to a core box comprising a lower shaping tool and an upper shaping tool between which a cavity is defined with the desired core shape (the material is transferred to the cavity). The shaping tools are arranged in a working position in which the material is transferred, and to that end the upper shaping tool moves by means of hydraulic actuation or the like, primarily due to its weight and therefore to the force required to perform said movement, guided by said structure, until being arranged in collaboration with the lower shaping tool to generate the cavity with the desired core shape. This type of movement is also referred to as carriage-like movement, as it is a linear movement guided by a structure. The lower shaping tool remains fixed in the structure of the machine.
Subsequently, a blowing head (or transfer tool) is transported to an operating position like a carriage (linear movement guided by a structure) by means of hydraulic actuation or the like primarily due to its substantial weight, and therefore to the force required to perform said movement, and guided by the structure of the machine, in which it is arranged on the shaping tools, and with said blowing head in said operating position, the material for making the core is transferred to the cavity generated between both shaping tools through the blowing head, generally comprising a plurality of nozzles for such purpose. The transfer is performed with the help of compressed air.
After transferring the material to the cavity formed between both shaping tools, the blowing head is removed from its operating position and a curing plate (a curing tool) moves to an operating position like a carriage (linear movement guided by a structure) by means of hydraulic actuation or the like, primarily due to its substantial weight and therefore to the force required to perform said movement, and guided by the structure of the machine, in which said curing plate is arranged on the shaping tools. With the curing plate in said operating position, the material previously transferred by the transfer tool is hardened, preferably by means of the application of a gas to the cavity generated between both shaping tools by means of said curing plate. The hardened material corresponds with the generated sand core.
Once the sand core is generated, the lower and upper shaping tools are separated from one another, such that the sand core is accessible, arranged on one of the shaping tools, so it can be handled (for example to convey it to the casting machine).
A sand core making machine is disclosed for example in EP0494762A2, and also in EP2907601A1 belonging to the applicant itself. The machine disclosed in EP2907601A1 comprises a transfer tool by means of which the material for making the core is transferred when said transfer tool is moved to an operating position, in particular over the cavity generated between a lower shaping tool and an upper shaping tool, by means of a carriage-like structure with guided linear movement. Once all the material (or the required material) has been unloaded, the transfer tool is removed from its operating position by means of the carriage-like structure, and simultaneously a curing tool is moved to an operating position by means of a respective carriage-like structure, position in which it is arranged on the material previously transferred with the transfer tool. By means of said curing tool, with said curing tool in its operating position, the material present in the cavity is hardened.
The patent document EP0284967A2 discloses a sand core making machine comprising a transfer tool for the core sand, and an articulated arm to rotate the transfer tool between an operation position and a none-operation position.